Joint constructions



April 1969 J. R. GAMBLE 3,437,554

JOINT CONS TRUCTIONS Filed Jan. 26, 1965 FIGZ.

INVENTOR v James R. Gamble WZMKM ATTORNEY United States Patent US. Cl.161206 Claims ABSTRACT OF THE DISCLOSURE An improved joint constructionis provided between a ceramic body and a surrounding metallic flangestructure secured thereto. A permanently-tacky resilient cushioninglayer of a silicone adhesive is applied to the ceramic body, so as to beinterposed between the ceramic body and the contiguous cement poured inthe intervening space between the inner ceramic body and the surroundingmetallic flange support member.

For a. rectangular ceramic body, additionally, corner pads of anasbestos material are pressed firmly to the corner positions of theceramic body and no alloy is permitted to penetrate behind the cornerpads.

This invention relates to joint constructions generally and, moreparticularly, to a joint construction between a ceramic body and anadjacently-disposed metallic support member.

This application is a continuation-in-part of my copending applicationfiled Dec. 22, 1964, Ser. No. 420,421 and now abandoned.

A general object of the invention is to provide an improved jointbetween a ceramic body, such as a porcelain body, and a metallic supporttherefor so that the ceramic body may be employed in an assembled unit.

As well known by those skilled in the art, in many types of equipment,such as switchgear, terminal bushings, lightning arresters, circuitbreakers, etc. there is need for use of a ceramic, or porcelain body forproviding a casing construction. In more detail, a circuit breaker mayrequire a hollow porcelain casing to surround the arc-extinguishingelements, and preferably, the hollow porcelain casing must have anannular end flange member secured to an extremity of the porcelaincasing so as to structurally attach the porcelain casing to a groundframe, an end line terminal member, etc. The support flange must beattached by a joint to the porcelain. casing which will resistvibration, shock and will not loosen over long periods of time.

As set forth recently in US. patent application filed Aug. 16, 1964,Ser. No. 387,919, now US. Patent 3,307,004 issued Feb. 28, 1967 toSamuel Bottonari, entitled, Circuit Interrupters, and assigned to theassignee of the instant application, the entire pole-support for acircuit interrupter to support the contact assemblies is provided by amolded porcelain support. To fixedly secure the porcelain pole-supportto a lower base frame, a rectangular metallic support flange is securedto the base portion of the porcelain pole support. This joint betweenthe pole-support and the encirling rectangular metallic flange supportmust resist shock stresses induced by breaker operation for long periodsof time. Reference may be had to Delevoy et al. Patents 3,086,097 and3,086,098 issued Apr. 16, 1963, for similar insulating pole-supportconstructions for circuit breakers, in which a rather complex integralmolded member which may be of a high-strength porcelain may be utilizedfor the main insulating frame of the circuit breaker. Rigid attachmentof such an insulating frame is required without the hazard that undershock conditions the main procelain frame will loosen and subjectoperating personnel to the hazard of electrical shock. To effect thisend, namely resisting indefinitely loosening of the metallic flangesupport from the main porcelain support body, the improved mechanicaljoint of the instant invention is directed. I have discovered that theinterposition of a somewhat resilient, or cushioning layer, within themetallic-porcelain joint proper has a remarkable effect of not onlyimproving shock resistance, but, more importantly, adding to themechanical strength and life of the joint.

Another object of the invention is an improved method for forming ametallic-porcelain joint.

Still a further object of the invention is the provision of an improvedjoint about an irregularly shaped porcelain body, that is a porcelainbody having one or more corner portions, which, as I have discovered,are more susceptible to the creation of failure cracks, which ultimatelyresult in breakdown of the joint proper.

Another object of the invention is to interpose a permanently-tacky andextremely viscous material, in thin layer form, in the joint between asupport flange and the adjacent supported porcelain body to resist shockand to improve mechanical strength.

The bonding material may be Portland cement, Mineralead, Babbit metal,or any other type of suitable cement.

Further objects and advantages will become apparent hereinafter withreference to the following detailed description, taken with reference tothe drawing, in which:

FIGURE 1 is a side elevational view of a porcelain pole-support for acircuit breaker of the type illustrated in the aforesaid US. Patent3,307,004, illustrating in broken-away fragmentary manner, the improvedjoint between the base of the porcelain pole-support and the surroundingmetallic flange support;

FIG. 2 is an inverted plan, or bottom view of the flanged porcelainpole-support, with a fragmentary crosssectional view being taken alongthe line II-II of FIG. 1, illustrating the corner padding construction;

FIG. 3 illustrates an end view of a lightning-arrester porcelain casingand the annular support flange secured thereto by the improved jointconstruction of the present invention,

FIG. 4 is a considerably enlarged fragmentary sectional view taken alongthe line IV-IV of FIG. 3; and,

FIG. 5 is a perspective view of the corner pad used in the improvedjoint construction.

With reference to the drawing and more particularly to FIG. 1 thereof,the reference numeral 1 designates a porcelain pole-support suitable forcircuit-breaker use. The porcelain pole-support 1 has molded thereinsupport openings 2, 3, through which contact foot and stud assemblies(not shown) may be fixedly mounted. The polesupport 1 is generally ofchannel-shaped configuration, having a connecting integral web portion4, through which the aforesaid support openings 2 and 3 are provided.

The base portion 5 of the porcelain pole-support 1 has a rectangularconfiguration, and encircling the aforesaid rectangular base portion '5is a metallic rectangular flange support member 7. The improved joint 8between the metallic support frame 7 and the porcelain body 1constitutes the essence of the present invention.

After the body 1 is molded and dried, a first glaze coating 9 is appliedover the entire body 1 with the exception of the bottom of the base 5,which has a wax layer applied thereto as this is the firing surface.

In the joint construction 8 of FIGS. 1 and 2, sand 10, having a meshsize of say 14-18 mesh, for example, is poured on a second glaze layer11 having a fish glue mixed therein, together with a certain part ofglycerin.

The glaze and fish-glue mixture 11 is painted by brush around thevertical base face portions 12 and while this glaze coating 11 is stillwet, the aforesaid sand 10 is poured by hand over such coating 11 and acertain portion of the sand 10 adheres thereto. Thus, prior to the kilnfiring operation of the porcelain body 1, a layer of sand 10 is providedall around the four vertical faces 12 of the rectangular base 5. As willbe obvious, the sand particles 10 assist in the formation of thesubsequent joint 8.

It is to be clearly understood that the aforesaid glaze and fish-gluemixture 11 is not necessary where the initial glaze layer 9 does not drytoo soon and the sand particles 10 may adhere to the initial glazecoating 9.

In practice however, due to the somewhat rapid drying of the initialglaze coating 9, it is preferable to apply the second glaze coating 11with fish glue additive and glycerin so that the sand 10 may have firmadherence to the base faces 12 of the porcelain body 1.

As is customary, the porcelain body 1 is fired in a kiln for a period ofapproximately a week, and when withdrawn from the kiln and slowly cooledis ready for the subsequent joint process of the instant invention.

After kiln firing, the sanded surfaces 12 of the porcelain body 1 arebrush coated with a layer of a tacky viscous material 13', which ispermanently tacky and provides a resilient cushioning layer in the joint8. The viscous and tacky coating material 13- is a plastic material,that is, over a wide range of temperatures, adherent, impervious tomoisture and capable of forming a smooth thin-layer. Suitableformulations will be set forth hereinafter. The coating 13 serves toreduce stresses at or adjacent the interface between the adjoiningBabbit metal, as described hereinafter. A coating material that ispermanently tacky is desirable in carrying out my invention. The coating13 must be capable of adhering to the base faces 12 of the base of theporcelain body 1 and also to the contiguously-poured Babbit metal, orMineralead, or highmelting point sulfur cement, or Portland cement.

In the joint construction 8 of FIGS. 1 and 2, the galvanized malleableiron flange support 7 and porcelain body 1 (following the firingoperation and coating 13 operation) is preheated to 250- -5 F. for aminimum of 8 hours preferably overnight, before assembly.

The porcelain body 1 is removed from the preheater immediately prior tothe assembly. Four impregnated asbestos tape sections 15 are placed inposition over the base corners and pressed firmly in place. The tapesections are cut from a .062 x 1.5 inch asbestos tape and impregnatedwith the silicone adhesive 13. The tape is dried and cut to l-inchlengths. The cut pieces are folded to .5 x 1.5. The tape sections 15 areplaced in the corner positions and pressed firmly into position. I havediscovered that it is important that the alloy 16 cannot penetratebehind them. Strength values were found to be reduced when the alloy wasallowed to penetrate behind the asbestos pads. The asbestos pads act toobviate the possibility of having stress concentrations on the cornersof the porcelain pole unit 1.

The malleable iron base 7 is taken from the preheater and tightened intoposition in a jig, not shown. The porcelain pole unit 1, together withthe corner padding 15 is also placed in a jig for correct alignment withrespect to the metallic flange support 7.

An alloy 16, such as Babbit metal at a temperature of say 700+25--10 F.is poured about the base 1 while the pole support 1 and the metallicflange 7 are still hot. The alloy 16 is cast in one pour.

The assembled device with the attached flange support 7 is removed fromthe jig fixtures and the assembly is permitted to cool slowly to roomtemperature.

The Babbit alloy 16 may have the following formulation: I l

Lead base Babbit metal in ingot or bar form as follows:

Chemical composition: Percent Tin 7.0-9.0 Antimony 13.0-15.0 Copper.50'.80 Impurities, total, max. .15 Aluminum and zinc None LeadRemainder Another formulation for an acceptable alloy is as follows:

Lead base Babbit metal in ingot or bar form as follows:

The improved joint construction of the present invention may be appliedto the porcelain-metallic flange constructions of lightning arrestercasings 20', such as shown in FIGS. 3 and 4 of the drawings. Referencemay be had to US. patent application Ser. No. 407,012 filed Oct. 28,1964, by Kennon et al. for a description of such a type of structure.

With reference to FIGS. 3 and 4 it will be noted that an annular supportflange ring 22 is attached to the extremity of a porcelain casing 24.The metallic ring 22 and upper surface 24a of the porcelain casing 24are coated with the resilient adhesive 13. Here, no sand is employed andthe ribs or corrugations 24b assist in providing a firmattachment.

After the flange support 22 and casing surface 24a have been coated withthe adhesive 13, the parts are placed in alignment jig devices and asuitable high-melting-point sulfur cement 25 is used to cast the partstogether. Here, the porcelain casing 24 is preheated, but not thesupport flange 22.

The formulation of the Mineralead cement is as follows:

Material: Content, percent Refined sulfur, min. 55 Inert aggregate 35-45*Plasticizer, max. 3

*Note.-Suitable nonvolatile plasticizer in suflicdent quantity so thatcement conforms to requirements of this specification.

(4) Inert aggregate composition-The chemical compositon of the inertaggregate shall conform to the followmg:

Chemical: Content, percent Carbon l.0-2.0 Si0 9-7 .098.5 A1 0 0.3-0.7 F60 0- CaO None MgO None K 0 None Na O None -NaCl or other inorganichalides None carrying out this invention is an organopolysiloxanecomposition comprising from to 70 percent by weight of a benzene solubleresin copolymer of SiO,,, units and R SiO units where R is an alkylradical of less than 4 carbon atoms or a phenyl radical, and where theratio of R SiO units to SiO units is from .621 to .911 inclusive, and 95to 30 percent by weight of a diorganopolysiloxane having the generalformula R' SiO, where R is methyl or phenyl and having viscosity of atleast 1,000,000 cs. at 25 C., and at least 90 percent of the totalnumber of -R and R radicals being alkyl.

organosiloxane adhesives particularly suitable for use in the practiceof the present invention are preferably a mixture of methylsiloxanes,one component being an elastomeric siloxane comprising repeating unitsin a chain terminated by (CH -Sigroups, wherein the ratio of (CH to Sigroups is close to 2, but may be either slightly greater than 2, orslightly less, and the other component being a resinous methylsiloxanehaving from at least one to substantially less than 2 methyl groups persilicon atom. From to 90% by weight of each component may be present inthe mixture. The molecular weights are such that a 37% solution of theorganopolysiloxanes in xylene has a viscosity of 3000 to 8000centipoises at 25 C. Catalysts for curing the mixture oforganopolysiloxanes comprise lead carboxyl salts, for example, leadnaphthenate, lead acetate and lead propionate, in amounts of from about0.001% to 2%. Benzenoid hydrocarbon solvents may be employed to dissolvethe organopolysiloxanes for instance benzene, toluene or xylene, toproduce solutions of from 30 to 40% concentration. A 38% to 40% solutiongives goods results.

EXAMPLE I A suitable formulation consists of 50 parts by weight of anorganosiloxane copolymer composed of s)a 1 a units, and SiO units havingan average of about 1.2 methyl units per silicon atom in the copolymer,50 parts of a dimethylsiloxane having a viscosity in excess of10,000,000 cs. at 25 C., having a plasticity of 55, and 2.5 parts ofbenzoyl peroxide. Lead naphthenate may be substituted for the benzoylperoxide in this example.

A coating material of this type retains its physical and chemicalproperties over a wide range of temperatures and where such ranges areattained in short periods of time and is particularly adapted for use incoating electrical members that are subjected to severe changes intemperature.

Other suitable silicon formulations are set forth in U.S. Patent2,736,721.

A particularly desirable adhesive coating 13 is a silicon adhesive soldby Dow Corning Coporation of Midland, Mich. under the trade name DowCorning 271 adhesive. This is a pressure-sensitive silicone adhesivewhich remains tacky and flexible at service temperature from -80 to over500 -F.

The improved joint construction of the present invention has resulted ina marked increase in cantilever strength. For example, using the type ofjoint construction of the present invention, the cantilever load thatwould cause failure increased from a range of 1600- 2900 pounds to arange of 4200 pounds to 6600 pounds. Also, the flexibility andcushioning effect provided by the silicon adhesive 13 results in adesirable increase of the pole-unit 1 to resist shock and vibrationstresses.

As an indication of the important commercial uses of the presentinvention, it is to be observed that approximately 6,*000 pole-units 1,incorporating the improved joint 8, have gone out into commercial use,and

6 have been found to satisfy a long-existing 'want for an insulatingsupport capable of resisting shock and vibration, and providing thedesirable insulating qualities which are afforded by the use ofporcelain. "The aforesaid figure is concerned only with circuit breakeractivity, and other uses, for example the lighting-arresterapplications, as set forth in FIGS. 3 and 4 constitute a furtherimportant active field of use for the present invention.

Although there has been set forth specific joint constructions, andmethods of providing the same, it is to be clearly understood that thesame were merely for the purpose of illustration, and that changes andmodifications may readily be made therein by those skilled in the art,without departing from the spirit and scope of the invention.

I claim as my invention:

1. An improved ceramic-metallic joint construction including a coatingof a silicon adhesive on the ceramic body for providing a permanentlyflexible layer, and an interposed cement between the ceramic body andthe surrounding metallic flange support.

2. A joint construction including a porcelain body and a surroundingmetallic support flange, a l to 15 mil coating of a silicone adhesive onthe porcelain body for a permanently flexible and resilient layer and aninterposed body of cement.

3. In combination, a porcelain body having one or more corner portions,a resilient corner pad for covering a corner portion in contiguousrelation to said corner portion, an adjacent metallic supporting flange,and a cement interposed .between the porcelain body and the metallicsupporting flange.

4. A porcelain-metallic joint including a porcelain body having asurface coating of a material which is an organopolysiloxane compositioncomprising from 5 to 70 percent by weight of a benzene soluble resincopolymer of SiO units and R SiO units where R is an alkyl radical ofless than 4 carbon atoms or a phenyl radical, and where the ratio of RSiO units to SiO units is from .6:1 to .9:1 inclusive, and 95 to 30percent by weight of a diorganopolysiloxane having the general formulaR' SiO, where R is methyl or phenyl and having a viscosity of at least1,000,000 cs. at 25 C., and at least percent of the total number of Rand R radicals being alkyl, a surrounding metallic flange support, and acement interposed between said surface coating and the surroundingmetallic flange support.

5. A porcelain-metallic joint including a porcelain body having asurface coat-ing of an adhesive material which has a formulationconsisting of 50 parts by weight of an organosiloxane copolymer composedof units, and Si0 units having an average of about 1.2 methyl units persilicon atom in the copolymer, 50 parts of a dimethylsiloxane having aviscosity in excess of 10,000,000 cs. at 25 C., having a plasticity of55, and 2.5 parts of benzoyl peroxide, a surrounding metallic flangesupport, and a cement interposed between said surface coating and thesurrounding metallic flange support.

6. The combination according to claim 3, wherein the resilient cornerpad is impregnated with a silicone adhesive material.

7. A porcelain-metallic joint including a porcelain casing and asurrounding metallic flange member, a coating of a silicone adhesive onthe confronting faces of both the porcelain casing and the surroundingmetallic flange member, and a cement interposed between the casing andflange member.

8. The method of providing a resilient porcelain-metallic jointincluding the steps of: coating the joint surface of the porcelain bodywith a layer of l to 15 mils of a silicone adhesive to provide apermanently resilient layer within the joint, and placing a cementwithin the interposed cavity between the porcelain body and thesurrounding metallic support flange member.

9. The process of claim 8, wherein the silicon adhesive is anorganopolysiloxane composition comprising from 5 to 70 percent by weightof a benzene soluble resin copolymer of Si units and R SiO units where Ris an alkyl radical of less than 4 carbon atoms or a phenyl radical andwhere the ratio of R SiO units to Si0 units is from .6:1 to .9:1inclusive, and 95 to 30 percent by weight of a diorganopolysiloxanehaving the general formula R SiO, where R is mehtyl or phenyl and havinga viscosity of at least 1,000,000 cs. at 25 C., and at least 90 percentof the total number of R and R radicals being alkyl.

10. The process of claim -8, wherein the silicone adhesive has asuitable formulation consisting of 50 parts of an organosiloxanecopolymer composed of units, and SiO units having an average of about1.2 methyl units per silicon atom in the copolymer, 50 parts of adimethylsiloxane having a viscosity in excess of 10,000,000 cs. at 25C., having a plasticity of 5S, and 2.5 parts of benzoyl peroxide.

11. The process of claim 8, wherein both the joint surfaces of theporcelain body and the surrounding metallic support flange member arecoated with the said silicone adhesive.

12. A porcelain-metallic joint including a porcelain body having asurface coating of an adhesive material which comprises a mixture offrom to 90% by weight of each of an elastomeric methylpolysiloxane and aresinous methylpolysiloxane and having a viscosity of from 3000 to 8000centipoises at 25 C. for a 37% solution in xylene, and up to 2% byweight of a lead carboxyl salt to catalyze the curing of the appliedcoating to an adherent elastic layer, a surrounding metallic flangesupport, and a mineral cement interposed between said surface coatingand the metallic flange element.

13. An improved ceramic-metallic joint construction including a coatingapplied to a ceramic body of an adhesive material which comprises amixture of from 10 to by weight of each of an elastomericmethylpolysiloxane and a resinous methylpolysiloxane and having aviscosity of from 3000 to 8000 centipoises at 25 C. for a 37% solutionin Xylene, and up to 2% by weight of a load carboxyl salt to catalyzethe curing of the applied coating to an adherent elastic layer, and aninterposed cement between the ceramic body and the surrounding metallicflange support.

14. The joint construction of claim 13, wherein the coating applied tothe ceramic body is 1 to 15 mils in thickness.

15. The process of claim 8, wherein the silicon adhesive is an adhesivematerial which comprises a mixture of from 10 to 90% by weight of eachof an elastomeric methylpolysiloxane and a resinous methylpolysiloxaneand having a viscosity of from 3000 to 8000 centipoises at 25 C. for a37% solution in xylene, and up to 2% by Weight of a load car-boxyl saltto catalyze the curing of the applied coating to an adherent elasticlayer.

References Cited UNITED STATES PATENTS 2,631,961 3/1953 Antheil 156-310X 3,071,217 1/1963 Gould 161---207 X 3,242,376 3/1966 Schultz 200144 XFOREIGN PATENTS 833,800 4/ 1960 Great Britain.

EARL M. BERGERT, Primary Examiner.

T. R. SAVOIE, Assistant Examiner.

US. Cl. X.R.

